Well? (: Do you believe in monogamy?

1. I have never cheated on someone
2. I've never cheated with someone (Not that I know of.)
-However, my first girlfriend kissed another girl and wrote romantic letters to another girl behind my back-
-My second girlfriend (towards the end) would delete all her texts, get blackout drunk, and I once saw a text pop up that said "I'll lion mount you" (Wtf?) (She'd get furious if I went near her phone, toward the end)
-And the last guy I dated, when I asked him if I was the only girl, said No. (At least he was honest)
-And I've seen a lot of old people at parties kiss and touch each other's wives as if it's nothing?
-I have had men with girlfriends/wives try to get with me. (They were rejected.)

I suppose this all bothers me because when I was little I'd watch fairy tales featuring monogamy (Yay Disney princesses!) and I wanted and still want that so bad! But I am continually slapped in the face by reality..

Not to mention I have seen a lot* of cheating and met a lot of polygamists lately

So what do you think? You think monogamy is real? Or an illusion?
(I mean monogamy as in ONE romantic/sexual partner, ONE person you kiss)